Underwater cameras, by their nature, are sealed against entry of water during use. One-time-use underwater cameras are also usable unsubmerged. While used in air, protection from entry of rain, dust, or the like, may also be desirable. Since access is not required for film loading, a one-time-use camera can be sealed air- and water-tightly during manufacture. This can be problematic if the one-time-use camera is left out in the sun. A sealed camera that is left out in the sun can develop a high internal pressure. This can cause damage to camera components. The water-tight seal may be lost, without any visible distortion of a housing or cover.
One solution to this problem is the use of a housing that can be repeatedly opened and closed. This is comparable to the use of a reusable camera with a housing or cover that is opened at least every time film is loaded or use of a separate underwater housing that is installed only for underwater use. The housing can be opened as necessary to prevent overpressurization. This solution is not desirable for one-time-use underwater cameras, which are intended for casual use without restrictive procedures.
Japanese patent publication JP 6-294992A, published Oct. 21, 1994, teaches a waterproof camera case that provides a valve that vents air (or other gas) to relieve excess internal pressure. The valve can also be used to evacuate air and add nitrogen at reduced pressure. This approach provides venting to reduce pressure, but adds one or more parts and some complexity. The valve also presents an additional risk of leakage.
U.S. Pat. No. 4,763,145 teaches a camera that adjusts internal air pressures to permit configuration changes such as moving a lens barrel between a wide-angle position and a telephoto position. Space within the camera for expansion and contraction is provided by a movable piston, elastomer member, or the like. A manual valve is optionally provided for venting.
U.S. Pat. No. 5,870,632 teaches a leakage detector which is used with a waterproof casing of a camera that is pressurized to greater than atmospheric pressure. The leak detector indicates if pressurization is decreased due to leakage.
These leakage detectors have the shortcoming of being relatively complex assemblies.
Two shot injection molding is a well-known technique that provides one-piece plastic castings that are made of different materials in different regions of the casting. The different materials are united by codiffusion of adjoining regions of the two different materials. During molding, conditions are selected such that the molecules of the two different regions diffuse together before solidification. The codiffused zones have interpenetrating polymer networks. (This is also referred to as xe2x80x9cmolecular entanglementxe2x80x9d.)
A variety of two shot molding techniques are known, such as those disclosed in U.S. Pat. Nos. 6,066,282; 4,460,534; 6,296,796; and 5,737,002. Among these techniques is the use of a hard engineering plastic for one of the regions and a tougher, but softer material such as an elastomer, for another region of the casting. EP 0 865 779 A1 discloses an orifice coupling that has an internal, soft wiper seal formed by two shot injection molding. The use of two shot molding for the housing of an underwater one-time-use camera is disclosed in U.S. Pat. No. 5,832,312.
U.S. Pat. No. 4,999,664 teaches an exposure control that responds automatically to water pressure when submerged.
It would thus be desirable to provide an improved pressurization indicator, housing, camera, and method in which the indicator is a simple, two-shot molded structure.
The invention is defined by the claims. The invention, in its broader aspects, provides a pressure indicator of an underwater camera housing has an indicator support surrounding an opening. An elastomer facing is united with the indicator support. The facing has a free region overlaying the opening. The free region has an inner surface and an outer surface. The free region is deflectable by a relative pressure differential between the inner and outer surfaces. Excessive inward excursion of the free region can be prevented by a backup.
It is an advantageous effect of the invention that an improved pressurization indicator, housing, camera, and method are provided in which the indicator is a simple, two-shot molded structure.